This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A. Specific Aims Specific Aim 1: Test the hypothesis that aging enhances the negative effects of high fat diet (HFD) on brain leptin signaling, metabolism and behavior. Specific Aim 2: Test the hypothesis that aging will impair the ability of the animal to reduce body adiposity and recover normal brain leptin signaling following cessation of a HFD. Specific Aim 3: Test the hypothesis that leptin protects against oxidative stress in hypothalamic and hippocampal neurons by enhancing antioxidant enzyme activity via NRF2 signaling. Specific Aim 4: Determine the functional interaction between leptin signaling and oxidative stress within areas of the hippocampus and hypothalamus.